The degreasing of machine parts has presented a special cleaning challenge since the use of greases for lubricating machine parts was conceived. Traditionally, the degreasing of machine parts has been accomplished using compositions with petroleum derived or halogenated hydrocarbon solvents or with aqueous compositions containing high levels of caustic and/or phosphates. Such compositions are either hazardous to use, and/or they leave residues that are environmental pollutants which are not readily or easily disposed of. Besides, many of the solvents and compositions are extremely flammable and must be used in carefully controlled environments designed to inhibit fire and explosion.
In recent times, it has been discovered that terpene-based aqueous degreasers may be used to replace the more hazardous compositions described above. Such aqueous cleaners are described, for example, in U.S. Pat. No. 4,414,128 which issued on Nov. 8, 1983 to Goffinet; U.S. Pat. No. 4,511,488 which issued on Apr. 16, 1985 to Matta; and, U.S. Pat. No. 5,679,628 which issued on Oct. 21, 1997 to Simpson et al. These patents describe various cleaning and degreasing compositions which include, as principle components, a terpene and water. A problem with each of the compositions is that they also include one or more constituents which are harmful to the environment. Furthermore, most of these compositions are relatively high in terpene concentration. While d-limonene is one of the most potent, yet easily biodegradable natural terpenes, it is a relatively expensive component of a degreasing composition. It is therefore desirable to provide an effective degreaser which includes a relatively low concentration of terpene in order to conserve costs. It is also desirable to provide a degreasing composition which is completely biodegradable in order to eliminate the introduction of persistent toxic residues into the environment.